Winding for an electrical machine

ABSTRACT

Winding for an electrical machine having an inductor with pole pitch τ p , having a plurality of groups of turns intercepting a fraction of a magnetic field, each group comprising a first subgroup of turns and a second subgroup of turns of same phase at a distance equal to τ p , the turns of the first subgroup being connected in such a way that a current may flow in same direction in all turns of said subgroup, the turns of the second subgroup being connected in such a way that a current may flow in same direction in all turns of said subgroup, a turn of the first subgroup being connected to a turn of the second subgroup in such a way that the direction of said current in the first group is opposite to the direction of the current in the second subgroup.

FIELD OF THE INVENTION

The invention relates to a winding for an electrical machine.

DESCRIPTION OF PRIOR ART

Electrical machines exist under many forms. These machines can begenerators, producing electrical energy from mechanical energy, ormotors, producing mechanical energy from electrical energy. Rotatingmachines have a rotor rotating around an axis in relation to a stator.Linear machines have a static element and a moving element movinglinearly with respect to the static element. The present inventionrelates to electrical machines having an inductor producing a magneticfield and an armature winding wherein currents may flow. When theinductor is the rotor of a rotating electrical machine and is apermanent magnet, no brushes are needed for accessing the current in thearmature winding. Rotating electrical machines may comprise an inductorproducing a magnetic field directed mainly radially, with a windinghaving a generally cylindrical shape. Rotating electrical machines mayalso comprise an inductor producing a field directed mainly axially,with a winding having a generally disc-shape. Linear electrical machinesmay comprise an inductor producing a magnetic field directed mainlyperpendicular to the direction of the movement and oriented towards thearmature winding, this winding having a generally rectangular shape.

A winding for a slotless brushless-DC motor (BLDC motor) is known from“B. Dehez, M. Markovic, Y. Perriard, “Analysis and comparison ofclassical and flex-PCB slotless windings in BLDC motors,” ElectricalMachines and Systems (ICEMS), 2012 15th International Conference on, pp.1-6, 21-24 Oct. 2012”. This document describes the general structure ofa BLDC motor. A comparison is made between a classic copper-wirewinding, and a Flex-PCB winding having a simple shape (a three segmenteither skewed (wave) or rhombic (lap) winding) showing a potential 30%improvement in power density of the Flex-PCB winding over the classiccopper-wire winding. However, no attempt is made at finding a designwith optimal performance.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a winding for anelectrical machine having an improved efficiency or/and an improvedtorque density (rotating machine) or force density (linear machine). Theefficiency may be defined as the ratio of delivered power to absorbedpower. In a motor, the delivered power is the mechanical power availableat the motor shaft (or Force X speed for a linear motor), and theabsorbed power is the electrical power absorbed by the winding. In agenerator, the delivered power is the electrical power provided at thewinding and the absorbed power is the mechanical power provided to theshaft (or Force X speed for a linear generator). The losses are mainlyrelated to the electrical resistance of the winding. It is therefore anobject of the present invention to provide a winding minimising theselosses, while delivering a given high power when used in an electricalmachine. The torque or force density may be defined as the ratio of thetorque or force, respectively produced by an electrical machine and itsweight. The weight of an electrical machine is mainly determined by theJoule losses arising in the armature windings. For a current of givenamplitude circulating in the armature windings, the Joule losses aredirectly proportional to their electrical resistance while the torque orforce is directly proportional to the amplitude of the magnetic fluxintercepted by these windings and generated by the inductor. It istherefore an object of the present invention to provide a windingminimising the electrical resistance, while maximising amplitude of themagnetic flux intercepted by these windings and generated by theinductor.

The invention is defined by the independent claims. The dependent claimsdefine advantageous embodiments.

According to a first aspect of the invention there is provided a windingfor an electrical machine adapted for interacting with an inductorstructure providing a sequence of at least one pair of north and southmagnetic poles along a length, producing a magnetic field, said polesbeing separated by a pole pitch distance τ_(p) along said length, thewinding comprising one or more phases, the number of phases being n. Thewinding is adapted for moving in relation to the inductor structurealong said length. The winding has a plurality of groups of pairs ofconductors, each pair of conductors forming a turn intercepting afraction of the magnetic field. A group comprises a first subgroup ofturns of one phase having a spread along said length inferior or equalto τ_(p)/n, and a second subgroup of turns of same phase having a spreadalong said length inferior or equal to τ_(p)/n, at a distance equal toτ_(p) from first subgroup along said length. The turns of the firstsubgroup are connected in such a way that a current may flow in samedirection in all turns of said subgroup, the turns of the secondsubgroup being connected in such a way that a current may flow in samedirection in all turns of said subgroup, a turn of the first subgroupbeing connected to a turn of the second subgroup in such a way that thedirection of said current in the first group is opposite to thedirection of the current in the second subgroup. The first subgroup andthe second subgroup may have same number t of turns.

Preferably, said pairs of conductors comprise first conductors arrangedin a first layer and second conductors arranged in a second layer.

Said first and second layers may be separated by an intermediate layer.The intermediate layer may advantageously be insulating. One extremityof a first conductor is connected to an extremity of a correspondingsecond conductor through an opening in said intermediate layer.

In a preferred embodiment of the invention, said first, intermediate andsecond layers are layers of a PCB.

In the lap version of the invention, each of said pairs of conductors ofa turn form a loop. The entry and exit terminal of the turns may be inclose vicinity to each other. The conductors of the winding may show aline of symmetry, the symmetry axis being a line along the length of theintermediate layer, at mid-height of the intermediate layer.

A conductor of the first layer of one turn may be extended along itslength and connected through said intermediate layer to a conductor ofthe second layer, having a corresponding extension, so as to form aconnection between two adjacent turns, the two adjacent turns being at adistance in the length direction.

In a first improvement of the invention, each of said first and secondsubgroup of turns having a number t of turns, first conductors of thefirst layer being numbered from 1 to t in the length direction, secondconductors of the second layer being also numbered from 1 to t in thelength direction, first conductor i of the first layer is connected atthe upper end of said conductor to second conductor t-i of the secondlayer through a horizontal shortcut connection extending along thelength direction, at decreasing heights, for i=1 to i=t−1; and firstconductor i of the first layer is connected at the lower end of saidconductor to second conductor t-i+1 of the second layer through ahorizontal shortcut connection extending along the length direction, atincreasing heights, for i=1 to i=t. Said horizontal shortcut connectionsmay be arranged in said first and/or in said second layer.

In a second improvement of the invention, each of said first and secondsubgroups of turns having a number t of turns, first conductors of afirst subgroup being numbered from 1 to t in the length direction,second conductors of the subsequent second subgroup being also numberedfrom 1 to t in the length direction;

first conductor i of the first layer is replaced by a vertical shortcutextending in the vertical direction for the extent of said conductoroverlapping second conductor 1 of the second layer, for i going from thefirst conductor having an overlap, to the last conductor t; andsecond conductor i of the second layer is replaced by a verticalshortcut extending in the vertical direction for the extent of saidconductor overlapping conductor t of the first layer, for i going fromthe first conductor 1 to the last conductor having an overlap. Thesevertical shortcut connections may be arranged in said first and/orsecond layer, except for shortcut number t of first subgroup andshortcut number 1 of second subgroup which are only in first and secondlayer respectively.

In the wave version of the invention, each of said pairs of conductorsof a turn form a wave. The entry and exit terminals of the turns may beat a distance near 2*τ_(p) along said length of each other. Theconductors may show a point of symmetry, the reflection point being atmid-height of the intermediate layer.

A plurality of turns may be connected in series and a plurality ofseries of turns may be arranged successively at a distance in the lengthdirection, a first conductor of the first layer of one turn of oneseries being extended along its length and connected through saidintermediate layer to a second conductor of a successive series of thesecond layer, having a corresponding extension, so as to form aconnection between two successive series, the two successive seriesbeing at a distance in the length direction.

In a preferred version of the invention, first conductors of the firstsubgroup of turns are interrupted at mid height and connected throughsaid intermediate layer with corresponding second conductors of thesecond subgroup, at both ends of said length, so as to form a continuouscircuit.

In said first improvement of the invention, a plurality of series ofturns are arranged successively at a distance in the length direction,said plurality of series is a number t of series,

adjacent conductors being numbered from 1 to t in both the first andsecond layer,and first conductor i of the first layer is connected at the upper endto second conductor t+1−i of the second layer through a horizontalshortcut connections extending along the length direction, at decreasingheights, for i=1 to i=t, and second conductor i of the second layerbeing connected at the lower end to first conductor t+1−i of the firstlayer through a horizontal shortcut connections extending along thelength direction, at increasing heights, for i=1 to i=t, except for oneof the said plurality of series where first conductor i of the firstlayer is connected to second conductor t-i of the second layer through ahorizontal shortcut connection extending along the length direction, atdecreasing heights, for i=1 to i=t−1, conductors t of the first andsecond layer being connected to terminals.

In said second improvement of the invention, wherein a plurality ofseries of turns are arranged successively at a distance in the lengthdirection, said plurality of series is a number t of series, adjacentconductors being numbered from 1 to t in the length in both the firstand second layer, the winding is obtainable by modifications of thewinding of the wave version of the invention, the modificationscomprising

-   -   providing a connection of part of first conductor number 1 of        first subgroup extending on upper part of intermediate layer to        part of second conductor number 1 of second subgroup extending        on lower part of intermediate layer, through said intermediate        layer, at mid-height of said intermediate layer;    -   redirecting respectively        -   (a) part of first conductors number 2 to number t−1 of said            first subgroup, extending on upper part of intermediate            layer up to the point of overlap with second conductor            number 1 of second subgroup to        -   (b) part of second conductors number 2 to number t−1 of            second subgroup extending on lower part of intermediate            layer from the point of overlap with first conductor number            1 of first subgroup        -   (c) through a vertical shortcut connection extending in a            vertical direction said a vertical shortcut connection being            in first and/or in second layer;    -   redirecting        -   (a) part of first conductor number t of said first subgroup,            extending on upper part of intermediate layer up to the            point of overlap with second conductor number 1 of second            subgroup to        -   (b) part of first conductor number 1 of first subgroup            extending on lower part of intermediate layer from the point            of overlap with second conductor number t of second subgroup        -   (c) through a vertical shortcut connection extending in a            vertical direction said a vertical shortcut connection being            in first layer;    -   Performing similar operations after a rotation of 180° around a        vertical axis being the vertical shortcut applied on first        conductor t.        The above connections and redirections, with respect to both the        wave and lap version of the winding, are such that a current        flowing in a conductor will flow to a conductor whereto it is        connected or redirected. Unused parts of conductors of the        original wave or lap winding wherefrom the winding according to        the second improvement are obtained are removed.

Preferably, in the winding according to the first and second improvementof the invention, i.e. the windings having vertical and/or horizontalshortcuts, these shortcuts may extend on first and second layer, exceptwhere explicitly not allowed. Having two shortcut conductors in parallelreduces the overall resistance of the winding, and therefore improvesthe efficiency. In these cases, a plurality of vias may be connectingsaid corresponding vertical and/or horizontal shortcut connection in thefirst and second layer.

Preferably, one or more windings are superimposed with an insulatinglayer being located between two superimposed windings.

According to a second aspect, the invention is related to the use ofthese windings in electrical machines. Windings in an elongatedconfiguration may be used in a linear electrical machine. When wound upin a direction perpendicular to the length, the linear electricalmachine may be a cylindrical winding travelling along a linear magnethaving a radial field, inside the cylinder. When the winding is wound upin the length direction, in a cylindrical configuration, the winding maybe used in a rotating electrical machine, having a radial field. Whenwound up in a disc-shaped form, in a flat configuration, the winding maybe used in a rotating electrical machine having an axial field.

SHORT DESCRIPTION OF THE DRAWINGS

These and further aspects of the invention will be explained in greaterdetail by way of examples and with reference to the accompanyingdrawings in which:

FIG. 1 is a schematic representation of a lap winding according to theprior art.

FIG. 2 is a schematic representation of a wave winding according to theprior art.

FIG. 3 is a schematic representation of a lap winding according to anembodiment of the invention.

FIG. 4 is a schematic representation of a wave winding according to anembodiment of the invention.

FIG. 5 is a schematic representation of a lap winding according to afirst improvement of the embodiment of the invention.

FIG. 6 is a schematic representation of a wave winding according to samefirst improvement of the embodiment of the invention.

FIG. 7 is a schematic representation of a lap winding according to asecond improvement of the embodiment of the invention.

FIG. 8 is a schematic representation of a wave winding according to samesecond improvement of the embodiment of the invention.

FIG. 9 is a schematic representation of a lap winding combining firstand second improvements of the embodiment of the invention.

FIG. 10 is a schematic representation of a wave winding combining firstand second improvement of the embodiment of the invention.

FIG. 11 is a schematic representation of a wave winding having a thirdimprovement of the embodiment of the invention.

FIG. 12 is a schematic representation of a wave winding having a thirdimprovement of the embodiment of the invention in combination with thefirst and second improvement of the invention.

FIG. 13 is a schematic representation of a lap winding combining firstand second improvement of the embodiment of the invention for use in arotating electrical machine having an axial field.

The drawings of the figures are neither drawn to scale nor proportioned.Generally, identical components are denoted by the same referencenumerals in the figures.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

In all the examples of the prior art and of the invention discussedherein, a first conductor 61, represented as a continuous line isconnected to a second conductor 62, represented as dashed lines so as toform a turn. Conductors 61, 62 may be straight lines, broken lines orcurves.

A pair of conductors 61, 62 of a turn may for a loop. In this case, theconductors may show a line of symmetry, with respect to a line passingthrough their midpoint, and form lap windings, as shown in FIGS. 1, 3,5, 7, and 9. The line at mid-height of the windings is represented onthe drawings as a dotted line at the left and right end of the windings.Alternatively, a pair of conductors 61, 62 of a turn may for a wave. Inthis case, the conductors may show a point of symmetry, and form wavewindings, as shown on FIGS. 2, 4, 6, 8, 10, 11 and 12. In a firstembodiment of the invention, the conductors may be wires or rodsinsulated from each other by many means known in the art. For example,the conductors may be coated with an insulating material. Also, theconductors may be wrapped around or in a support that may be insulating.In a second embodiment of the invention, the first conductors 61 are inone layer and the second conductors 62 are in a second layer, preferablyseparated from each other by an insulating layer. These conductors maybe obtained by cutting out from sheets of conductive material. Thecut-out may be performed by known techniques such as mechanical cutting,laser cutting or chemical attack. The connection of a first conductor 61of the first layer to a second conductor 62 of the second layer may thenbe obtained by an opening in the insulating layer through which theconductors are contacted or soldered. These conductors may also betracks printed on both sides of a printed-circuit board (PCB). Theconnection of a first conductor 61 on a first side of the PCB to asecond conductor 62 on the second side of the PCB may then be realisedby a via 43, i.e. a hole through the PCB, containing conductivematerial. The term “via” is used herein for designating the differentconnecting means of a first conductor 61 to a second conductor 62. Vias43 are represented on the figures by a little circle. All thesesolutions are well knows in the art. In all the examples discussed, thelength direction will be the direction from left to right of the figureand the height direction, the direction from the bottom to the top ofthe figure. The windings are represented as flat structures, as thiswill be the case for linear motors or generators. The windings may alsobe wound up in a cylindrical fashion one or more times along the lengthdirection, for use in a rotating electrical machine having a radialmagnetic field. The windings may also be wound up in a cylindricalfashion one or more times along a direction perpendicular to the lengthdirection, for use in a linear tubular electrical machine having aradial magnetic field. The winding may also be wound up in a discfashion, for use in an electrical machine having an axial magneticfield. The “length” is then to be understood as the azimuthal angulardistance. When the winding is wound up more than one time, or when aplurality of windings are superimposed, a fourth insulating, andoptionally adhesive, sheet may be inserted between each winding layer inorder to avoid unwanted electrical short circuits between windingturns/loops.

FIG. 1 is a schematic representation of an example of a lap winding foran electrical machine according to the prior art. A first conductor 61having a line symmetry with respect to a line represented by the dots atthe left and at the right of the figure is connected to a secondconductor 62 through a via 43 at the bottom of the figure to form aturn. A plurality of such turns (in this example 10 turns) are connectedin series so as to form a group of turns, having a current entryterminal 44 and a current exit terminal 45. Successive turns aredisplaced with respect to each other in the length direction. This maybe obtained by extending the first and second conductors beyond theirheight L1 up to a height L2, and connecting a turn to an adjacent turnthrough a via 43 at the height L2. FIG. 1 displays a three phasewinding, a first phase being drawn in bold line and the other two phasesin thin lines. The inductor structure providing a magnetic field isrepresented schematically as a bar, and shows two North poles and twoSouth poles. This inductor structure is represented for clarity at thebottom of the winding, but is overlapping the winding, so that the turnsintercept the magnetic field. The electrical machine is designed in sucha manner that the winding may move in relation to the magnet structurein the length direction. The separation distance in the length directionbetween a north pole and a south pole is τ_(p). As can be seen in FIG.1, the distance between two successive groups of a phase in aconventional winding is 2 τ_(p) such that these two groups intercept thesame field, both in sign and amplitude. The extent of a group in thelength direction is 2 τ_(p) divided by the number of phases. Thiscondition is required for preventing an overlap of successive groups ofturns. Current exit terminal 45 of one group may be connected to currententry terminal 44 of a successive group of same phase, so that currentsin the conductors flow in the directions suggested by the arrows. Theprior art winding of FIG. 1 is discussed more in detail at paragraphs[0030] and FIG. 7a of WO2014/207174.

FIG. 2 is a schematic representation of an example of a winding for anelectrical machine according to the prior art, similar to FIG. 1 withthe difference that the conductors 61, 62 form wave turns. Theconductors 61, 62 are formed as straight lines, but may also be formedas polygonal lines or curves, as shown in other examples. Here, as inFIG. 1, the distance between two groups is 2 τ_(p), and the extent of agroup in the length direction is 2 τ_(p)/3

FIG. 3 is a schematic representation of a lap winding according to anembodiment of the invention. With respect to the winding of FIG. 1, thewinding of FIG. 3 has been modified as follows: the group of turns hasbeen divided in a first subgroup 81 of turns, and a second subgroup ofturns 82. Second subgroup 82 is located from first subgroup 81 at adistance τ_(p) in the length direction. The extent of a subgroup in thelength direction is τ_(p) divided by the number of phases, i.e half theextent of a group in the winding of FIG. 1. This condition is requiredfor preventing an overlap of successive subgroups of turns. Currententry/exit terminals 44/45 of the first subgroup, and 44′/45′ of thesecond subgroup are in opposite orders so that a current flowing inconductor 61 of first subgroup would flow in opposite direction incorresponding conductor 61′ of second subgroup. This condition can bemet when current exit terminal 45 of one subgroup is connected tocurrent entry terminal 44′ of another successive subgroup of same phase.As can be seen on FIG. 3, when a first subgroup intercepts the field ofa north pole, a subsequent second subgroup of same phase intercepts thefield of a south pole. The inventors have determined that this windingaccording to the invention has an torque or force density improved byapproximately 15% with respect to corresponding winding of the prior artof FIG. 1 having same characteristics, for a three-phase winding. Thisimprovement results from the fact that the turns of a phase intercept amagnetic flux, and therefore generate an electromotive force, whosephase spreading is reduced by a factor of two with respect to the priorart winding. The spreading factor linking the electromotive forceamplitude of a winding to the electromotive force amplitude of one turnmultiplied by the number of turns and given by the mathematical formula:

2 sin(α/2)/α

where α is the maximum phase difference, increases therefore from 0.827to 0.955, in a three phase winding. The phase spreading is reduced from120 to 60 electrical degrees.

FIG. 4 is a schematic representation of a wave winding according to anembodiment of the invention. The modifications of the winding of FIG. 1to the winding of FIG. 3 have been applied similarly to the winding ofFIG. 2. Same improvement of efficiency is obtained.

FIG. 5 is a schematic representation of a lap winding according to afirst improvement of the embodiment of the invention. The improvementlies in the manner of interconnecting turns of a subgroup with respectto the manner of interconnecting the turns of a subgroup in FIG. 3. Withreference to FIG. 5, first conductor 61, numbered 3 in the firstsubgroup is connected to second conductor numbered 2 in the samesubgroup through a horizontal shortcut connection 46. For reducing thephase resistance, this horizontal shortcut connection may be made inparallel in the first layer and in the second layer. Similar shortcutconnections are made for all turns of a subgroup both at the top and atthe bottom of the winding. As is well known by the man skilled in theart, only the component of currents perpendicular to the relativemovement (i.e. axial currents in a cylindrical electrical machine) willgenerate a torque or force in a motor. Therefore, in the nearlytriangular regions at the bottom and at the top of the winding of FIG. 3where first conductors 61 if the front layer and second conductors 62 ofthe second layer overlap, the resulting torque will be nil. Thisexplains why the improved mode of inter-turn connection, represented inFIG. 5 represents no loss in torque or force when the electrical machineis a motor while reduces the phase resistance. For a same geometry andcurrents, the winding of FIG. 5 will produce the same torque or force asthe winding of FIG. 3. Compared to the winding of FIG. 3, the winding ofFIG. 5 has shorter tracks, and therefore a reduced phase resistanceR_(ph). For the same reasons, when the electrical machine is agenerator, the emf generated with the winding of FIG. 3 and FIG. 5 willbe equivalent.

FIG. 6 is a schematic representation of a wave winding according to samefirst improvement of the embodiment of the invention. The improvementcorresponds to the modifications made to the winding of FIG. 3 forobtaining the winding of FIG. 5 but applied to the winding of FIG. 4.Horizontal shortcut connections 46 reduce the overall length of theconductors, without reducing the torque or force of the electricalmachine. The applicants have observed that, for a conventional design,the resulting torque or force density is improved by more than 10% withrespect to the winding without horizontal shortcuts.

FIG. 7 is a schematic representation of a lap winding according to asecond improvement of the embodiment of the invention. The improvementlies in a modification of the shape of conductors 61, 62 in the medianregion of their height. With reference to FIG. 7, as an example, firstconductor 61, numbered 3 in the first subgroup 81 is shortcut beginningfrom the point of overlap with conductor 62 numbered 1 of secondsubgroup 82, with a vertical shortcut connection 47.

Second conductor 62 of second subgroup 82 is also shortcut with avertical shortcut connection 47′ from the point of overlap with the lastconductor 61 of preceding first subgroup (conductor number 2 in theexample shown). Except for the last vertical shortcut of the firstsubgroup and first vertical shortcut of the second subgroup, theseshortcuts may extend in parallel in the first and second layer, whichfurther reduces the phase resistance. The last shortcut of the firstsubgroup and the first vertical shortcut of the second subgroup overlap,and, being part of different circuits, may not be combined in parallel,but must remain in the first and second layer respectively. For reasonssimilar to the reasons explained in relation to the horizontal shortcutsand FIG. 5, the winding of FIG. 7 will produce same torque or force asthe corresponding winding of FIG. 3 without vertical shortcut. It has bedetermined, that, for the conductor shape of FIG. 7, the resultingtorque or force efficiency is improved by more than 1% with respect tothe winding of FIG. 3, without vertical shortcuts.

FIG. 8 is a schematic representation of a wave winding according to samesecond improvement of the embodiment of the invention. The improvementcorresponds to the modifications made to the winding of FIG. 3 forobtaining the winding of FIG. 7, but applied to the winding of FIG. 4.Vertical shortcut connections 47 reduce the overall length andresistance of the winding, without reducing the torque or force of theelectrical machine

FIGS. 9 and 10 are schematic representations of a lap and a wavewinding, respectively, combining first and second improvements of theembodiment of the invention, where the conductors have three linearsegments. This example shows that the invention and its improvementsapply similarly to windings where the conductors are straight lines,broken lines or curves.

The conception of a wave winding according to the second improvement ofthe invention (i.e. having the vertical shortcuts) will be described bydescribing the modifications to be performed on the winding of FIG. 4for obtaining the winding of FIG. 10, and focusing only on the verticalshortcut improvement, located in a diamond (lozenge) shaped area atmid-height of the winding.

First conductors 61 (continuous lines) of first subgroup are numberedsequentially from left to right and noted 61/1 to 61/t (t being equal to5 in FIG. 10). Similarly, second conductors 62′ (represented as dashedlines) of second subgroup are numbered 62′/1 to 62′/t.In a first modification (a), first conductor 61/1 is interrupted atmid-height of the winding, and connected through a via to the part ofconductor 62′/1 on the lower part of the winding. The remaining parts ofconductors 61/1 and 62′/1 will be discussed below.In a second modification (b), upper parts of conductors 61/2 to 61/t−1are kept up to the point where they overlap second conductor 62′/1 ofsecond group. From that point of overlap, they are interrupted andprolonged downwards by a vertical shortcut 47 up to the point whereconductor 62′/2 to 62′/t−1 overlap conductor 61/1. From that secondpoint of overlap, the vertical shortcuts are connected to the parts ofconductors 62/′2 to 62′/t−1 extending downwards, respectively.In a third modification (c), upper part of conductor 61/t is kept up tothe point where it overlaps second conductor 62′/1 of second group. Fromthat point of overlap, it is interrupted and prolonged downwards by avertical shortcut 47 up to the point where conductor 62′/t overlapsconductor 61/1. From that second point of overlap, the verticalshortcuts are connected to the part of first conductor 61/1 of firstgroup, extending downwards.Unused parts of conductors of original, unmodified winding are removed.Vertical shortcuts 2 to t−1 may extend in parallel on both sides ofintermediate layer, thereby reducing the resistance of the winding. Lastvertical shortcut t may extend only on one side. Modifications (a) (b)and (c) address the left hand side of the diamond region of FIG. 10.Similar modifications are performed for the right hand side of thediamond region of FIG. 10: the winding is rotated 180° around thevertical diagonal of the diamond, and same connections and redirectionsare performed on conductors now occupying locations of former conductorsSame operations may be performed on all diamonds occurring in thewinding. It can be seen from the drawing that e.g. the currents inconductors 61/1 to 61/t−1 of first subgroup in upper part of winding,and flowing downwards, will flow in the natural direction, alsodownwards, in conductors 62′/1 to 62′/t−1, producing the same motor orgenerator effect as with the winding of FIG. 4, but with a reducedresistance, and therefore an improved efficiency.In the present discussion “to overlap” it is to be understood as meaning“to be on same position but on different sides of an intermediate layer”

All examples discussed in relation to FIGS. 3 to 10 have been describedwithout discussing the connections at the left and right ends of thewinding. For the lap windings of FIGS. 3, 5, 7, and 9, the situation issimple: each of the subgroups form coils, each having one current entryterminal 44 and current exit terminal 45. These may be connected toexternal means or interconnected so as to form a number of phases eachhaving a current entry terminal and a current exit terminal. The windingmay be of any length and have a plurality of groups of turns and may bewound up in a cylindrical fashion, with an insulating layer between twofolds, in such a way that corresponding groups and subgroups of samephase overlap. In the case of a PCB winding, all of the conductors,including the interconnections between subgroup at the top height of thePCB may be produced with a single PCB, without requiring any additionalwiring.

In the wave winding of FIG. 4, the second conductors 62 at the righthand end may be connected to corresponding first conductors 61 at theleft hand end of the winding. This may be performed with external wiringor additional tracks at the top of the PCB. FIGS. 11 and 12 showexamples of a third improvement of the invention where the need forthese external wiring or additional tracks is avoided. Referring to FIG.11, a conductor 61 of the first subgroup 81 of turns in the first layer,at the right hand end of the winding is interrupted at mid height of theintermediate layer and connected through said intermediate layer withvia 43 to corresponding lower half of conductor 62 of the secondsubgroup 82 in the other layer. This is performed for all conductors ofthis subgroup, and is performed in a similar fashion at the left handside of the winding. This results in having for each phase a closedcircuit having current entry terminal 44 and current exit terminal 45.The resulting winding can be produced as a single PCB, without requiringany additional wiring or connections. Although FIG. 11 shows a windinghaving three turns in each phase and each subgroup, a winding having anarbitrary number of turns may be produced, according to the needs of theelectrical machine for which it is intended. FIG. 12 shows an example ofa winding having same end-wraps of conductors in a winding having bothhorizontal and vertical shortcuts. The winding of FIG. 12 combines allimprovements of the invention.

FIG. 13 is a schematic representation of a lap winding combining firstand second improvement of the embodiment of the invention for use in arotating electrical machine having an axial field. This winding isadapted for interacting with an inductor having two north poles and twosouth poles producing a magnetic field oriented along the axis, i.e.perpendicularly to the figure. The poles are distributed at 90 degreesfrom each other. The winding has two first subgroups 81 and two secondsubgroups 82 at 90 degrees angular distance from each other.

The present invention has been described in terms of specificembodiments, which are illustrative of the invention and not to beconstrued as limiting. More generally, it will be appreciated by personsskilled in the art that the present invention is not limited by what hasbeen particularly shown and/or described hereinabove.

Reference numerals in the claims do not limit their protective scope.Use of the verbs “to comprise”, “to include”, “to be composed of”, orany other variant, as well as their respective conjugations, does notexclude the presence of elements other than those stated. Use of thearticle “a”, “an” or “the” preceding an element does not exclude thepresence of a plurality of such elements.

The invention may also be described as follows: the invention provides awinding for an electrical machine adapted for interacting with aninductor structure providing a sequence of at least one pair of northand south magnetic poles along a length, producing a magnetic field,said poles being separated by a pole pitch distance τ_(p) along saidlength. The winding may comprise one or more phases, be adapted formoving in relation to the inductor structure along said length, and havea plurality of groups of pairs of conductors, each pair of conductorsforming a turn intercepting a fraction of said magnetic field. Accordingto the invention, a first subgroup of turns of one phase have a spreadalong the length inferior or equal to τ_(p)/n, a second subgroup ofturns of same phase have a spread along said length inferior or equal toτ_(p)/n, at a distance equal to τ_(p) along said length, the turns ofthe first subgroup being connected in such a way that a current may flowin same direction in all turns of said subgroup, the turns of the secondsubgroup being connected in such a way that a current may flow in samedirection in all turns of said subgroup, a turn of the first subgroupbeing connected to a turn of the second subgroup in such a way that thedirection of said current in the first group is opposite to thedirection of the current in the second subgroup. The first subgroup andthe second subgroup may have the same number t of turns.

1-20. (canceled)
 21. A winding for an electrical machine adapted forinteracting with an inductor structure providing a sequence of at leastone pair of north and south magnetic poles along a length, producing amagnetic field, the poles being separated by a pole pitch distance r_(p)along the length, the winding comprising: one or more phases, the numberof phases being n; and a plurality of groups of pairs of conductors,each pair of conductors forming a turn intercepting a fraction of themagnetic field, wherein a first group of the plurality of groupsincludes: a first subgroup of turns of one phase having a spread alongthe length inferior or equal to τ_(p)/n; and a second subgroup of turnsof same phase having a spread along the length inferior or equal toτ_(p)/n, at a distance equal to τ_(p) from first subgroup along thelength, the turns of the first subgroup being connected such that acurrent may flow in same direction in all turns of the first subgroup,the turns of the second subgroup being connected such that a current mayflow in same direction in all turns of the second subgroup, and a turnof the first subgroup being connected to a turn of the second subgroupsuch that the direction of the current in the first subgroup is oppositeto the direction of the current in the second subgroup, and wherein thewinding is adapted for moving in relation to the inductor structurealong the length.
 22. The winding according to claim 21, the firstsubgroup and the second subgroup having same number t of turns.
 23. Thewinding according to claim 21, a first conductor being arranged in afirst layer and a second conductor being arranged in a second layer. 24.The winding according to claim 23, the first and second layer beingseparated by an intermediate layer, the intermediate layer having aheight perpendicular to the length, an extremity of the first conductorbeing connected to an extremity of the second conductor through anopening in the intermediate layer.
 25. The winding according to claim 24wherein the first, intermediate, and second layers are layers of a PCB.26. The winding according to claim 24, wherein each of the pairsconductors of a turn form a loop.
 27. The winding according to claim 26,wherein a conductor of the first layer of one turn is extended along itslength and connected through the intermediate layer to a conductor ofthe second layer having a corresponding extension to form a connectionbetween two adjacent turns, the two adjacent turns being at a distancein the length direction.
 28. The winding according to claim 26, whereineach of the first and second subgroups of turns have a number t ofturns, first conductors of the first layer being numbered from 1 to t inthe length direction, second conductors of the second layer being alsonumbered from 1 to t in the length direction, and a first conductor i ofthe first layer being connected at the upper end of the first conductori to a second conductor t-i of the second layer through a horizontalshortcut connection extending along the length direction, at decreasingheights, for i=1 to i=t−1; and the first conductor i of the first layerbeing connected at the lower end of the intermediate layer to a secondconductor t-i+1 of the second layer through a horizontal shortcutconnection extending along the length direction of the intermediatelayer, at increasing heights, for i=1 to i=t, the horizontal shortcutconnections being in at least one of the first layer or the secondlayer.
 29. The winding according to claim 26, wherein each of the firstand second subgroup of turns have a number t of turns, first conductorsof a first subgroup being numbered from 1 to t in the length direction,second conductors of the subsequent second subgroup also being numberedfrom 1 to t in the length direction; first conductor i of the firstlayer being replaced by a first vertical shortcut extending in avertical direction for an extent of the first conductor i overlapping asecond conductor 1 of the second layer, for i going from the firstconductor i having an overlap to a last conductor t; second conductor iof the second layer being replaced by a second vertical shortcutextending in the vertical direction for an extent of the secondconductor i overlapping conductor t of the first layer, for i going fromthe first conductor 1 to the last conductor having an overlap; the firstand second vertical shortcut connections being in at least one of thefirst layer or the second layer, except for shortcut number t of thefirst subgroup and shortcut number 1 of the second subgroup, which arein the first layer and the second layer respectively.
 30. The windingaccording to claim 24, wherein each of the pairs of conductors form aturn form a wave.
 31. The winding according to claim 30, wherein aplurality of turns are connected in series and a plurality of series ofturns are arranged successively at a distance in the length direction, afirst conductor of the first layer of one turn of one series is extendedalong its length and connected through the intermediate layer to asecond conductor of a successive series of the second layer, having acorresponding extension, so as to form a connection between twosuccessive series, the two successive series being at a distance in thelength direction.
 32. The winding according to claim 30, wherein firstconductors of the first subgroup of turns are interrupted at mid heightand connected through the intermediate layer with corresponding secondconductors of the second subgroup, at both ends of the length to form acontinuous circuit.
 33. The winding according to claim 30, wherein aplurality of series of turns are arranged successively at a distance inthe length direction, the plurality of series is a number t of series,adjacent conductors being numbered from 1 to t in both the first andsecond layer, and first conductors 1 to t of the first layer areconnected at the upper end to second conductors t to 1 respectively ofthe second layer through t horizontal shortcut connections extendingalong the length direction, at decreasing heights, and second conductors1 to t of the second layer being connected at the lower end to firstconductor t to 1 of the first layer through a horizontal shortcutconnections extending along the length direction, at increasing heights,except for one of the plurality of series where first conductors 1 tot−1 of the first layer are connected at the upper end to secondconductors t−1 to 1 respectively of the second layer through t−1horizontal shortcut connections extending along the length direction, atdecreasing heights, conductors t of the first and second layer beingconnected to terminals.
 34. The winding of claim 30, wherein a pluralityof series of turns are arranged successively at a distance in the lengthdirection, the plurality of series is a number t of series, adjacentconductors being numbered from 1 to t in the length direction in boththe first and second layer, obtainable by: providing a connection ofpart of the first conductor of the first subgroup extending on upperpart of the intermediate layer to part of the second conductor of thesecond subgroup extending on lower part of the intermediate layer,through the intermediate layer, at mid-height of the intermediate layer;redirecting respectively (a) part of first conductors 2 to t−1 of thefirst subgroup extending on an upper part of the intermediate layer upto a point of overlap with a second conductor 1 of the second subgroupto (b) part of second conductors 2 to t−1 of the second subgroupextending on the lower part of the intermediate layer from a point ofoverlap with a first conductor 1 of first subgroup (c) through avertical shortcut connection extending in a vertical direction, thevertical shortcut connection being in at least one of the first layer orthe second layer; redirecting (a) part of a first conductor t of thefirst subgroup extending on the upper part of the intermediate layer upto the point of overlap with the second conductor 1 of the secondsubgroup to (b) part of the first conductor 1 of the first subgroupextending on the lower part of the intermediate layer from the point ofoverlap with a second conductor t of the second subgroup (c) through thevertical shortcut connection extending in the vertical direction, thevertical shortcut connection being in at least one of the first layer orthe second layer for conductors 2 to t−1 and in the first layer only forconductor t; and performing same operations after a rotation of 180°around a vertical axis, the vertical shortcut being applied on firstconductor t.
 35. The winding according to claim 28, wherein a pluralityof vias connect at least one of corresponding vertical or horizontalshortcut connections in the first and second layer of the intermediatelayer.
 36. Use of the winding of claim 21, where the winding is in anelongated configuration, in a linear electrical machine.
 37. The useaccording to claim 36, where the winding is wound up in a directionperpendicular to the length.
 38. Use of the winding of claim 21, wherethe winding is wound up in the length direction, in a cylindricalconfiguration, in a rotating electrical machine.
 39. Use of the windingof claim 21, where the winding is wound up in a disc-shaped form, in aflat configuration, in a rotating electrical machine having an axialfield.
 40. Use of the winding of claim 21, wherein one or more windingsare superposed with an insulating layer being located between twosuperposed windings.